I have been using OpenOCD along with GDB on some ARM Cortex-M3 projects and started wondering what could be arranged along these lines with the BBB. This is just "recon" information, I have not actually followed through with any of this.
Note that the original Beaglebone (the Beaglebone White) offers JTAG via FTDI serial over USB in some way. It also has the pads for the 20 pin connector on the bottom of the PCB. One has to suspect that JTAG via serial would be pretty slow, but who knows.
The Flyswatter2 is a $89 item. Note that this is considered an inexpensive JTAG tool. The cable and adapter to attach it to the BBB is another $39, so you are talking $128 to get set up to do JTAG with your BBB. With this, you run OpenOCD, GDB, and go to town. A painful comparison with buying an STLINK V2 for $5 to do the same thing with an ARM Cortex-M3.
The last 2 links above discuss using the BBB itself as a bus-pirate like tool. The reverse of what I am interested in doing just now, but interesting for future reference.
Tom's Computer Info / email@example.com